KVM: x86/xen: register vcpu time info region

Allow the Xen emulated guest the ability to register secondary
vcpu time information. On Xen guests this is used in order to be
mapped to userspace and hence allow vdso gettimeofday to work.
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

arch/x86/include/asm/kvm_host.h

@@ -535,7 +535,9 @@ struct kvm_vcpu_hv {
 struct kvm_vcpu_xen {
 	u64 hypercall_rip;
 	bool vcpu_info_set;
+	bool vcpu_time_info_set;
 	struct gfn_to_hva_cache vcpu_info_cache;
+	struct gfn_to_hva_cache vcpu_time_info_cache;
 };
 
 struct kvm_vcpu_arch {

arch/x86/kvm/x86.c

@@ -2757,6 +2757,8 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 	if (vcpu->xen.vcpu_info_set)
 		kvm_setup_pvclock_page(v, &vcpu->xen.vcpu_info_cache,
 				       offsetof(struct compat_vcpu_info, time));
+	if (vcpu->xen.vcpu_time_info_set)
+		kvm_setup_pvclock_page(v, &vcpu->xen.vcpu_time_info_cache, 0);
 	if (v == kvm_get_vcpu(v->kvm, 0))
 		kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock);
 	return 0;

arch/x86/kvm/xen.c

@@ -141,6 +141,17 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		}
 		break;
 
+	case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
+		r = kvm_gfn_to_hva_cache_init(vcpu->kvm,
+					      &vcpu->arch.xen.vcpu_time_info_cache,
+					      data->u.gpa,
+					      sizeof(struct pvclock_vcpu_time_info));
+		if (!r) {
+			vcpu->arch.xen.vcpu_time_info_set = true;
+			kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
+		}
+		break;
+
 	default:
 		break;
 	}
@@ -164,6 +175,13 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
 		}
 		break;
 
+	case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
+		if (vcpu->arch.xen.vcpu_time_info_set) {
+			data->u.gpa = vcpu->arch.xen.vcpu_time_info_cache.gpa;
+			r = 0;
+		}
+		break;
+
 	default:
 		break;
 	}

include/uapi/linux/kvm.h

@@ -1620,6 +1620,7 @@ struct kvm_xen_vcpu_attr {
 };
 
 #define KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO	0x0
+#define KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO	0x1
 
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {